DESCRIPTION (investigator's abstract): Although the implicit motive approach to human motivation has spawned a staggering amount of basic and applied research over the past 50 years, the processes at the core of implicit motives have received comparatively little attention in research. Specifically, there is a lack of empirical data elucidating why individuals high in a given motive seek to attain a motive-specific incentive in the first place and what consequences incentive consummation has for their behavior. For the case of the implicit power motive, the Principal Investigator has developed a model which posits that having impact - the incentive associated with the power motive - is rewarding for individuals high in implicit power motivation and reinforces behavior that was instrumental for having impact Importantly, because the power motive operates outside of a person's conscious awareness, individuals may be unaware of motive-based processes of reward and reinforcement These processes will therefore be assessed with objective behavioral and psychophysiological measures in the proposed research. Specifically, the gonadal steroid hormone testosterone is hypothesized to be an indicator of power motivation reward and to increase in high-power individuals in response to having impact. Enhanced implicit learning of behavior that was instrumental in having impact is hypothesized to reflect reinforcement in high-power individuals. Furthermore, the model states that power motivation reward, as indicated by surging testosterone, mediates power motivation reinforcement, as indicated by enhanced implicit learning. Three experimental studies on the role of personalized power motivation, a subtype of the implicit power motive, in winning or losing a dominance contest mark a first step towards validating this model. Study 1 will provide an initial test of the model in men, while Study 2 explores to which extent it also holds for women, in which estradiol may play a more important role than testosterone in power motivation reward. Study 3 will test whether the hypothesized rewarding effect of testosterone can be potentiated by a caffeine-induced increase of incentive motivation. In addition, the role of facial aflective expressions as indicators of power motivation reward and the time course of the hypothesized power motivation reward and reinforcement effects will be explored in these studies.